Various tests that are conducted on components associated with semiconductor devices include a burn-in test that involves application of a voltage for a prolonged period of time (from a few hours to tens of hours) at a high temperature (approximately 150° C.). Because conducting a burn-in test on a package level is not efficient, it is more desirable to carrying out a burn-in test of a wafer level (by using a wafer having a diameter of 200 mm, for instance). In such a wafer level burn-in test, an electroconductive contact probe capable of simultaneously accessing a plurality of points is required.
Each contact unit that is used in the electroconductive contact probe is desired to have a structure that can accommodate variations in the height of the electrodes on the wafer by applying the needle member to the corresponding electrode in a resilient manner, and such an example is illustrated in FIG. 8. As shown in the drawing, a stepped holder hole 2 is formed across the thickness of a support member 21 in the form of a plate member, and an electroconductive needle member 23 is received in a small diameter hole 2a of each holder hole 2 so as to be moveable into and out of the holder hole 2 while a large diameter hole 2b of the holder hole 2 receives an electroconductive coil spring 24. The needle member 23 is provided with a radial flange 23a received in the large diameter hole 2b and one end of the coil spring 24 is wrapped around a stem portion 23b extending from the radial flange 23a so that the needle member 23 is resiliently urged by the coil spring 24. The other end of the coil spring 24 resiliently engages a corresponding terminal 25a of a circuit board 25 placed over the support member 21. These terminals 25a are connected to an electric circuit of the testing device.
By arranging such electroconductive contact units in the support member in a mutually parallel relationship, a contact probe capable of simultaneously accessing a plurality of points can be obtained. By applying the tip of each needle member 23 of the contact probe to the corresponding electrode 26a of the wafer 26 (object to be tested) so that the electric testing on a wafer level can be carried out.
To simultaneously access a plurality of electrodes 26a on a wafer 26, it is necessary that a same number of electroconductive contact units are provided in the support member in the same arrangement as the electrodes 26a on the wafer 26. Thus, a contact probe may be required to have a large number of contact units in a highly dense arrangement in a planar support member. However, owing to the combined pressure from the contact units, the positional accuracy of the contact units could be impaired owing to the warping or other deformation of the support member. In such a case, the positional errors in the contact points may create a serious problem.
As a countermeasure against such a problem, it is proposed in Japanese patent application 2000-33443 by the same applicant to incorporate a metallic reinforcing member in the support member made of plastic material by insert molding. Such an example is illustrated in FIG. 9. Small diameter holes are formed in a support member 28 incorporated with a reinforcing member 27, and each receive a stem portion of one of a pair of electroconductive needle members 28, both of which are intended to be moveable, so as to be moveable into and out of the hole. The coil spring 30 and the other electroconductive needle member 29 are provided in a large diameter hole and a stepped hole provided in the remaining plastic support members 32 and 33 which are laminated one over another. According to this arrangement, owing to the increased mechanical strength of the support member 28 by virtue of the reinforcing member 27, positional errors such as those mentioned above can be avoided.
However, as the frequency of the test signals rises, the contact probe is required to be adapted to such high frequency signals. It can be accomplished by reducing the total length (length of the signal path), and it requires the thickness of the support member (axial length of the contact probe) to be reduced accordingly. As it means a decrease in the thickness of both the support member and reinforcing member, the mechanical strength of the support member may be undesirably reduced.
When the support member is formed with plastic material and insert molded with a reinforcing member as described above, the thickness of the plastic material that covers the reinforcing member has to be reduced. Therefore, as the thickness of the support member is reduced, the proportion of the plastic material in the overall thickness of the support member tends to be increased, and this imposes a limit to an effort to minimize the thickness of the support member.